The HUI mode in the Automap Server was originally introduce for Nocturn users, because the Nocturn do not have templates system like the SL, and there was no way of controlling DAW such as Logic and Pro Tools.
Hence now SL users has a choice between the two.
Logic HUI, using template 38, this emulates a Mackie HUI control surface; whereas Logic Automap, using template 39, is dedicated control surface written for the SL.
The main differences are you can freely re-assign controls the way you like in Logic HUI, whereas the control in Logic Automap is fixed and cannot be edited. Logic Automap has both mixer and instrument mode whereas Logic HUI only control the mixer. Plus you do not get actual value feedback in HUI mode, display is only between 0-127; whereas in Logic Automap, you get actual value display, such as fader level in dB for example.